1. Field of the Invention
The present invention relates to an ASK communication device for making data communication between a master station and at least one slave station by using an ASK (Amplitude Shift Keying) mode.
2. Description of the Related Art
A communication mode using an ASK mode is known as a mode of connecting a master station and slave stations through bus lines and making data communication among the respective stations (refer to Japanese Patent Laid-Open Publication No. 2002-152291).
FIG. 1 is a timing chart showing timing of transmitting and receiving data in a conventional communication mode using the ASK. A horizontal axis direction represents a time base. A vertical axis direction in FIG. 1(a) represents amplitude of a carrier signal S superposed on the bus line. The vertical axis direction in FIG. 1(b) represents the transmission/reception timing of the data in the master station. The vertical axis direction in FIGS. 1(c) to 1(e) represents the transmission/reception timing of the data in three slave stations. Moreover, reference symbols Tx and Rx shown in FIG. 1 denote transmission and reception, respectively. The master station has ID0 as an ID thereof, and the three slave stations individually have IDs 1 to 3 as IDs thereof.
As shown in FIG. 1(a), the master station outputs ID data of a station serving as a transmission source, and when the ID0 as the ID of the master station is designated, outputs, to the bus line, communication data transmitted therefrom to each slave station. Moreover, as shown in FIGS. 1(c) to 1(e), when the communication data is outputted from, each slave station to the bus line, the master station receives the communication data thus outputted.
Moreover, as shown in FIG. 1(c), when the slave station having the ID1 is designated by the master station, the communication data transmitted by the slave station of the ID1 to the other slave stations and the master station is outputted to the bus line.
In a similar way, in FIGS. 1(d) and 1(e), transmission data is outputted to the bus line from the slave stations of the ID2 and the ID3. By such operations, the data communication can be sequentially made among the master station and the respective slave stations.